I'm going to omit names and places in the following account.
With a gliding "Silver C", and the necessary written exams passed (barely) I asked to fly with the Chief of a training establishment to go for the PPL, as it was rumored he was experienced in doing that particular conversion, needing only 8 or 10 hours to accomplish in those days.
I think he was of the opinion I was a pain in the butt, and he didn't really want to fly with me. It was my first flight in a Cessna 152, I was too ignorant to make sure I was strapped in correctly, able to reach the controls comfortably. I also mentioned I was nervous about spinning.....
The day was not completely VFR, we ascended through some broken cu, to the practice area. I did turns, etc etc. He seemed impatient, in a hurry to get it over with. So after 20 minutes, he said "I have control!" and put the Aerobat into a truly nasty spin. 3 turns, and handed it back to me on the downwind leg. I think he really wanted to discourage me from flying with him again, it certainly had that effect. Made a point after that, NOT of spin avoidance, but Chief avoidance! and completed the training with an eager younger instructor.
Not only certain instructors should be avoided, but certain aircraft as well.
We do a lot of spin training in gliders. There are some types with excellent safety records. And there are other types.